There is a multiplicity of problems connected with the use of such energy for power generation. The variable nature of wind speed and wave height, and the relatively infrequency of adequately strong winds or waves in preferred areas of habitation mean that without storing the power generated at irregular and mostly relatively low levels, a wind or water wave generator of economic size is scarcely ever able to meet the maximum demand on it. And of course storage of electrical energy is in itself problematical and expensive. On the other hand, since strong winds and high waves do happen, however infrequently, special measures are required to protect the installation, largely because the electric generator, if it is designed for average wind conditions or for normal waves, cannot absorb the very much higher power levels in high winds or waves. The power output of a wind wheel, for example, can be proportional to the cube of the wind speed. Largely on account of this fact, windmills have been designed which accommodate higher-than-average wind speeds by a loss of efficiency--the so-called Cretan windmill, with fabric sails that flap and lose lift at higher wind speeds is an example in which the speed limitation is inherent in the design. Other types of wind wheel have mechanisms, which can be automatic, for adjusting the angle of attack of the blades, and, of course, the friction brake is often resorted to. Using a generator sufficiently large to absorb high wind power such as is only infrequently encountered would involve high capital costs, and incur heavy losses due to the inefficiency of the generator at the lower, average speeds. Similar considerations clearly apply to wave power generators.
Wind generators, for example for domestic purposes, have a further disadvantage in that they must be kept quite separate from the mains supply, so that mains power cannot be used to supplement the wind generator power during high local demand periods or periods of low wind, nor, without expensive phase and voltage matching equipment, can they be used to feed back into the mains ("selling" electricity back to the power station, running the meter backwards) when local demand does not absorb the entire wind generated supply.
The present invention provides a method and apparatus for wind power generation in which this last mentioned disadvantage can be eliminated, and in which many other disadvantages are avoided or substantially reduced.